1. Field of the Invention
The present invention relates to an ionization device for removing electricity charge in a charged body that is either positively or negatively charged.
2. Description of the Related Art
Static electricity removal (removal of electricity), such as cleanup in a clean room and prevention of static charge of suspended particulates, is performed in order to control static electricity in the air, and corona discharge ionization devices are widely used for removing electricity in a noncontact manner.
A typical corona discharge electricity removing device causes corona discharge by applying either high voltage direct current or high voltage alternate current from a high voltage source to a needle electrode for discharge. FIG. 23 shows a schematic view of such an electricity removing device. The electricity removing device shown in this figure is provided with a discharge electrode 1 for causing corona discharge, a high voltage power supply unit 2 connected to an alternate current source, and a coupling capacitor 3 connecting the discharge electrode 1 with the high voltage power supply unit 2. The electricity removing device drives a high voltage transformer 2A which is the high voltage power supply unit 2 using alternate current source and applies high voltage to the discharge electrode 1 to cause corona discharge. The air surrounding the discharge electrode 1 is ionized due to the corona discharge, thereby generating either plus or minus ions. The ions in the ionized air are carried to an object item by blown with air by such as a fan provided for the electricity removing device. By neutralizing potential of the charged electricity of the object item with positive ions and negative ions, the electrical charge accumulated on the object item becomes closer to zero and removed.
A positive or negative ion flow generated by the electricity removing device and flowing in the air can be considered as current between a high voltage source and a ground. That is, the current flowing from the high voltage source to the ground corresponds to the negative ion flow, and the current flowing from the ground to the high voltage generating unit corresponds to the positive ion flow. As a result of such an interaction between the ion flow and the current, when an amount of positive ions generated by the electricity removing device equals to an amount of negative ions by the electricity removing device, the current is neutralized and amounts to zero. Therefore, by maintaining a balance between the amounts of the generated positive and negative ions, the electricity removing device can correctly perform removal of electricity.
For example, a so-called bar-type electricity remover has been known as a conventional ionization device as shown in FIG. 24 to FIG. 27. FIG. 24 to FIG. 27 show an ionization device; FIG. 24 is a perspective view illustrating an appearance of the ionization device, FIG. 25 is an exploded perspective view, FIG. 26 is a cross-sectional view, and FIG. 27 is a block diagram. The ionization device illustrated by these drawings is constituted by a discharge electrode bar. Such as a high voltage unit 213 is provided in an upper area within a main body casing 10, and an air supply unit 211 supplying air that carries ions is provided in a lower area of the main body casing 10. When an electrode assembly 236 is mounted to the air supply unit 211, a cutting contact segment 259 of a high voltage plate 258 is brought into contact with an upper end surface of a needle electrode 212. An area including a contact portion of the needle electrode 212 and the cutting contact segment 259 forms an enclosed space in the air supply unit 211, that is an enclosed space S2 isolated and independent from a main air channel S1 and a cylindrical branch air channel 245, by a tip end portion of a tubular portion with smaller inner diameter 240 of an electrode assembly 236 fitting into a first sleeve 229 of a supporting plate.
Patent Document 1: Japanese Unexamined Patent Publication No. 2002-216996
Different capabilities for removing electricity are required depending on an environment in which the electricity removing device is used. Specifically, the number of discharge electrodes is determined for each area from which electricity is required to be removed. However, providing separate discharge electrode bars for different areas with different numbers of required discharge electrodes poses problems such as requiring respective new designs and increase in cost. Therefore, providing an electricity removing device having the desired number of discharge electrodes by coupling a plurality of discharge electrode bars having several discharge electrodes is commonly employed.
However, the conventional discharge electrode bar is relatively heavy in weight because many metal components are used, and thus, a mechanical reinforcement is required to some extent in order to maintain strength at a coupling portion. In order to maintain the strength, it is necessary to use such as an additional metal component for a coupling member, resulting in a problem that an increased size and weight of an entire device.
One conceivable way to address the above problems is to reinforce a coupling structure. However, when rigidity of the main body casing is not sufficient, this method is insufficient and the main body casing itself is required to be reinforced with metal. This can cause increase in length and weight of the casing. In recent years, especially, a demand for an ionization device provided with an increased number of discharge electrodes and improved capability of electricity removal that can be applied to a large-scale apparatus is increasing. Further, because a supply channel for air that carries charged ions also becomes longer when the ionization device becomes longer, it becomes difficult to supply air sufficiently and evenly to each discharge electrode along the length. Moreover, there is a problem in securing safety.